1. Technical Field
The present invention relates to a biometric authentication system and a biometric authentication method for performing identity authentication using biometric information obtained by acquiring an image of a blood vessel or the like.
2. Related Art
In order to verify that a user is an authorized one, biometric authentication in which biometric information such as a fingerprint, an iris, or a vein pattern of the authorized user is used has been performed in recent years (for example, see Japanese Patent No. 3549795). Accordingly, various biometric information acquisition systems have been used. Known among these biometric information acquisition systems are ones including a light source for radiating light and a light receptor for receiving light. Such a system obtains biometric information by causing the light source to emit light onto a living body, causing the light receptor to receive the light from the living body, and converting the received light into an electric signal.
As our environment is becoming flooded with electronic apparatuses requiring authentication, such as cell phones and personal computers, large-size, high power-consuming biometric information acquisition systems have been avoided. On the other hand, higher authentication accuracies have been demanded as people raise their security awareness; therefore, improvements in accuracy of biometric information are also required.
When performing biometric authentication, a comparison is made between features of a part of a living body that are previously registered and data obtained by measuring a living body when performing authentication and then a determination whether they are matched is made. Methods for measuring a living body include transmission type in which light transmitted through a living body is received and reflection type in which light reflected by a living body is received. These types differ in positional relation among a light source, a light receptor, and a living body interposed therebetween. If a living body is measured when registering authentication data or when performing authentication using the authentication data, a transmission image or a reflection image significantly deteriorates due to strong dispersion inside the living body or on the body surface. Therefore, no more than the presence or absence of an image of the target blood vessel or a rough position of the blood vessel is currently known from an image obtained using a typical transmission or reflection method. If an appropriate point spread function (PSF) is obtained, the deterioration of an image due to dispersion is alleviated by performing deconvolution. However, if an image acquisition system employing, for example, percutaneous fluoroscopy is used, there occurs a problem that the PSF significantly varies depending on the depth of the targeted blood vessel and thus the authentication result varies.